The shadowy work of Britain's oldest known artist has been rediscovered after 120 centuries, in a find that turns the history of the country's first inhabitants upside down.

Specialist detective work in a dank Midlands cave has shattered the 300-year-old belief that no British cave paintings exist, in contrast to the wealth of stylised animals, birds and tribesmen found on the continent.

"It was an amazing moment when we traced the lines - invisible without special lighting - and found we were looking at an ibex-like creature," said Paul Pettitt of Oxford University, who made the discovery with British and Spanish colleagues.

"It fills in one of the biggest gaps in Britain's history, and puts an end to the debate about whether ice age inhabitants had cultural contacts with the rest of Europe."

The ibex, along with scratched birds and geometrical patterns in Church Hole, Mother Grundy's Parlour and Robin Hood caves at Creswell Crags in Nottinghamshire, has been dated to 12,000BC, largely through the "semi-twisted perspective" style of the unknown artist.

"It is a beautiful piece of work by someone with real feeling for the animal," said Paul Bahn, another member of the team and Britain's leading ice age art specialist.

"The delicate line of the animal's throat and the feeling of movement compare with the best in the world. Cave artists from France and Spain, the home of Europe's most celebrated paintings, would have recognised a fellow master."

The archaeologists are confident that they have not been fooled like predecessors whose claims to the same momentous discovery of ice age art ended with red faces.

Among blunders in the past was the sensation over marks in a Welsh coastal cave which turned out to be the work of a fisherman touching up his boat and drying the paintbrush.

"We can date these through the style," said Sergio Ripoli, of Uned University, Madrid, who has worked on international commissions preserving cave art in France and Portugal.

He added: "But we also know that we are not dealing with fakers. Graffiti from the last century is still raw, but the ibex, the birds and the other drawings have been patinated over time. It is as though the lines of the drawing have been varnished."

The graffiti helped for years to obscure the paintings from visitors, who would also look in vain through the gloom without specialist lighting. The cave floor in Church Hole, the home of the ibex, has also fallen by several feet over the centuries, partly thanks to Victorian explorers whose tools included dynamite.

The paintings will not be open to the public because of their fragile condition, but virtual reality tours of the caves - part of a warren in Creswell's picturesque limestone gorge - are being arranged.

English Heritage and the Heritage Lottery Fund are financing further searches in the area and in similar limestone caves, where more ice age art is almost certainly hidden.